What hazards are associated with the APU during an in-flight or ground incident?

What hazards are associated with the APU during an in-flight or ground incident?

• A. Potential re-ignition, external fuel ignition sources, and possible explosion when overheated.
• B. It poses no hazard
• C. It can operate as a fire extinguisher
• D. It reduces fuel loads

Answer: (A)

APUs sit at the heat and fuel interface in an aircraft, so they can significantly influence a fire scenario. The exhaust and hot surfaces from the APU can re-ignite flammable vapors or residual fuel in the area if a fire is already present, making a suppression effort flare up again instead of staying out. The APU also provides an ignition source beyond the original fire because its exhaust plume and exposed hot components can ignite spilled fuel or vapors outside the unit itself. If the APU overheats, the intense heat and pressure can lead to a failure of components or rupture, creating a potential explosion. So, in both in-flight and ground incidents, the hazards related to the APU include the possibility of re-ignition, external ignition of fuels, and explosion when overheated.

APUs sit at the heat and fuel interface in an aircraft, so they can significantly influence a fire scenario. The exhaust and hot surfaces from the APU can re-ignite flammable vapors or residual fuel in the area if a fire is already present, making a suppression effort flare up again instead of staying out. The APU also provides an ignition source beyond the original fire because its exhaust plume and exposed hot components can ignite spilled fuel or vapors outside the unit itself. If the APU overheats, the intense heat and pressure can lead to a failure of components or rupture, creating a potential explosion. So, in both in-flight and ground incidents, the hazards related to the APU include the possibility of re-ignition, external ignition of fuels, and explosion when overheated.